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      1 /*
      2  * Copyright (C) 2010 Apple Inc. All Rights Reserved.
      3  *
      4  * Redistribution and use in source and binary forms, with or without
      5  * modification, are permitted provided that the following conditions
      6  * are met:
      7  * 1. Redistributions of source code must retain the above copyright
      8  *    notice, this list of conditions and the following disclaimer.
      9  * 2. Redistributions in binary form must reproduce the above copyright
     10  *    notice, this list of conditions and the following disclaimer in the
     11  *    documentation and/or other materials provided with the distribution.
     12  *
     13  * THIS SOFTWARE IS PROVIDED BY APPLE COMPUTER, INC. ``AS IS'' AND ANY
     14  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     15  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     16  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE COMPUTER, INC. OR
     17  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
     18  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
     19  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
     20  * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
     21  * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     22  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
     23  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     24  *
     25  */
     26 
     27 #ifndef StackBounds_h
     28 #define StackBounds_h
     29 
     30 namespace WTF {
     31 
     32 class StackBounds {
     33     // recursionCheck() / recursionLimit() tests (by default)
     34     // that we are at least this far from the end of the stack.
     35     const static size_t s_defaultAvailabilityDelta = 4096;
     36 
     37 public:
     38     StackBounds()
     39         : m_origin(0)
     40         , m_bound(0)
     41     {
     42     }
     43 
     44     static StackBounds currentThreadStackBounds()
     45     {
     46         StackBounds bounds;
     47         bounds.initialize();
     48         bounds.checkConsistency();
     49         return bounds;
     50     }
     51 
     52     void* origin() const
     53     {
     54         ASSERT(m_origin);
     55         return m_origin;
     56     }
     57 
     58     void* current() const
     59     {
     60         checkConsistency();
     61         void* currentPosition = &currentPosition;
     62         return currentPosition;
     63     }
     64 
     65     void* recursionLimit(size_t minAvailableDelta = s_defaultAvailabilityDelta) const
     66     {
     67         checkConsistency();
     68         return isGrowingDownward()
     69             ? static_cast<char*>(m_bound) + minAvailableDelta
     70             : static_cast<char*>(m_bound) - minAvailableDelta;
     71     }
     72 
     73     bool recursionCheck(size_t minAvailableDelta = s_defaultAvailabilityDelta) const
     74     {
     75         checkConsistency();
     76         return isGrowingDownward()
     77             ? current() >= recursionLimit(minAvailableDelta)
     78             : current() <= recursionLimit(minAvailableDelta);
     79     }
     80 
     81 private:
     82     void initialize();
     83 
     84 
     85     bool isGrowingDownward() const
     86     {
     87         ASSERT(m_origin && m_bound);
     88 #if OS(WINCE)
     89         return m_origin > m_bound;
     90 #else
     91         return true;
     92 #endif
     93     }
     94 
     95     void checkConsistency() const
     96     {
     97 #if !ASSERT_DISABLED
     98         void* currentPosition = &currentPosition;
     99         ASSERT(m_origin != m_bound);
    100         ASSERT(isGrowingDownward()
    101             ? (currentPosition < m_origin && currentPosition > m_bound)
    102             : (currentPosition > m_origin && currentPosition < m_bound));
    103 #endif
    104     }
    105 
    106     void* m_origin;
    107     void* m_bound;
    108 };
    109 
    110 } // namespace WTF
    111 
    112 using WTF::StackBounds;
    113 
    114 #endif
    115